domain mapping plugin cannot be activated

when I try to activate this plugin it says:

Plugin could not be activated because it triggered a fatal error.

Warning: require_once(extra/wpmudev-dash-notification.php) [function.require-once]: failed to open stream: No such file or directory in /home/cnckevin/public_html/wp-content/plugins/domain-mapping.php on line 44

Fatal error: require_once() [function.require]: Failed opening required 'extra/wpmudev-dash-notification.php' (include_path='.:disappointed:usr/lib/php:disappointed:usr/local/lib/php') in /home/cnckevin/public_html/wp-content/plugins/domain-mapping.php on line 44